1. Field of the Invention
This invention relates to a method and apparatus for thermal transportation utilizing ice slurry moved through a pipe.
2. Description of the Prior Art
Prior art methods of thermal transportation and storage using ice slurry include adding antifreeze protein to a liquid and cooling the liquid to produce an ice slurry that is then stored, or transported by being pumped through a pipe. Methods involving simply cooling a liquid utilize just the sensible heat of the liquid, so the quantity of heat that is transported and stored is relatively small. Also, in the case of methods that just use solid ice, it is difficult to pump the ice through pipes. Moreover, in the case of the prior art methods in which ice is produced from a liquid, since latent heat is accumulated during the phase change from liquid to ice, a large quantity of heat can be transported, and the good flow properties of the ice slurry, which exhibits good response property during thermal utilization, enables it to be pumped through piping.
However, making the ice readily subjectable to secondary recrystallization (growth of the ice crystals) degrades the response property exhibited when the ice slurry is to be dissolved for thermal utilization. Because this can cause clogging of the piping, this method is not suitable for thermal storage for extended periods or for long-distance transportation applications. In the prior art methods described above the addition of antifreeze protein to the liquid enables recrystallization of the ice to be suppressed, making the methods also suitable for thermal storage for extended periods and for long-distance transportation. Antifreeze protein is protein obtained from fish in waters close to the polar regions. It is this protein that prevents the blood of the fish from freezing. However, antifreeze protein is very costly. This means that it is expensive to use ice slurry in which recrystallization is suppressed for thermal transportation.
The present inventors have already proposed a method and apparatus for thermal transportation and storage using a silane coupling agent, alkane thiol or fatty acids in place of antifreeze protein [Papers (B) of The Japan Society of Mechanical Engineers, vol. 65, No. 630, pp 53-58 (1999-2)]. However, the method and apparatus using synthetic high polymers had a number of problems, including cost, toxicity, corrosiveness and solubility in water, which were enough to keep the method and apparatus from being practicable. More specifically, with respect to the silane coupling agent, the cost was not low enough, in addition to which the material was toxic and not soluble enough in water. Similarly, the corrosiveness of the fatty acids was a problem, as was their toxicity and lack of sufficient solubility in water. With respect also to the alkane thiol, solubility in water posed a problem, and there were also questions relating to the toxicity and corrosiveness of the substance.
This invention was accomplished to overcome the foregoing problems and has as an object to provide a method and apparatus for thermal transportation that lowers the cost of thermal transportation using ice slurry in which recrystallization is suppressed, and also uses materials having good properties in terms of toxicity, corrosiveness and solubility in water.
For attaining this object, the present invention provides a thermal transportation method utilizing polyvinyl alcohol, the method comprising adding vpolyvinyl alcohol to a liquid, cooling the liquid to which the polyvinyl alcohol has been added to form an ice slurry, and pumping the ice slurry through a pipe.
The above object is also attained by an apparatus for thermal transportation utilizing polyvinyl alcohol, the apparatus comprising a liquid to which polyvinyl alcohol has been added, a freezing means for cooling the liquid to which the polyvinyl alcohol has been added to form an ice slurry, a pipe for transporting the liquid containing the ice slurry, and a pump for moving the liquid in the pipe.
Thus, to achieve its object, the invention uses polyvinyl alcohol instead of the antifreeze protein, silane coupling agent, alkane thiol or fatty acids used in the prior art. The polyvinyl alcohol has the effect of suppressing recrystallization of the ice slurry and is extremely cheap, being about {fraction (1/20,000)} the price of antifreeze protein. Moreover, polyvinyl alcohol is neither toxic nor corrosive, and exhibits excellent solubility in water. Thus, it enables thermal transportation using ice slurry in which recrystallization is suppressed that is highly stable and highly reliable, and low in cost.
Further features of the invention, its nature and various advantages will become more apparent from the accompanying drawings and following detailed description of the invention.